Step-by-step explanation:
Given that,
The voltages across them are 40,50 and 60 volts respectively, and the charge on each condenser is 6×10⁻⁸ C.
(a) Capacitance of capacitor 1,

Capacitance of capacitor 2,

Capacitance of capacitor 3,

(b) The equivalent capacitance in series combination is :

Hence, this is the required solution.